Permanent topical antistats

ABSTRACT

Antistatic compositions for topical application to substrates, which comprise 
     (a) a polymer of less than about 20,000 molecular weight consisting essentially of, in polymerized form, about 10 to 99 mole % alkylene oxide, of 2 to 4 carbon atoms, about 1 to 90 mole % glycidol and about 0 to 15 mole % of the glycidyl ester of a fatty acid of about 2 to 20 carbon atoms and about 0 to 15 mole % of the glycidyl monoester of a polycarboxylic acid, 
     (b) a curing agent capable of cross-linking the polymer by reaction with the primary hydroxyl groups of the glycidol units, such as melamine-formaldehyde condensates, dialdehydes, polycarboxylic acids and their anhydrides, epoxy resins (polyepoxides), polyisocyanates, and the like and 
     (c) a catalyst for the curing reaction, such as zinc fluoroborate, a sulfonic acid, phosphoric acid, ammonium sulfate or the like.

This application is a continuation-in-part of Ser. No. 553,713 filed2/27/75 now abandoned.

CROSS-REFERENCE TO RELATED APPLICATIONS

Copending applications Ser. No. 444,078 filed Feb. 20, 1974, now U.S.Pat. No. 4,014,854, and Ser. No. 633,539 filed Nov. 19, 1975, as acontinuation-in-part of Ser. No. 466,099 filed May 2, 1974, and nowabandoned, by three of us (Stevens, Sexton and Corson), disclosepolymers suitable for use in the present invention and methods formaking such polymers. For such disclosure, they are hereby incorporatedherein by reference.

BACKGROUND OF THE INVENTION

Textiles containing acrylic, polyester or polyamide fibers and films ofsuch thermoplastics are prone to develop objectionable static electriccharges. An excellent general review of various antistatic compositionsand processes for ameliorating the static problem is that of John E.Clark, Am. Dyestuff Reporter, Feb. 27, 1967, pp. 37-43.

Topical antistats, i.e., those designed for surface application toreduce static charge build-up, have been unsatisfactory for use ontextiles because of defects such as lack of permanence, unpleasant hand(greasy feel, harshness, etc.), or undesirable appearance or odor, etc.Desirably, such antistats should be such that they can be applied froman aqueous medium and then rendered wash-resistant by a simpleafter-treatment. They should not impart odor, color, greasiness,unpleasant hand, dullness or other undesirable property to the substratenor adversely affect its normal utility.

SUMMARY OF THE INVENTION

The antistatic composition of the invention comprises:

(a) a polymer of less than about 20,000 molecular weight consistingessentially of units of the formula

    --CH.sub.2 CHRO--

where in about 10 to 99%, preferably about 50 to 95%, of the units R isH, CH₃ or C₂ H₅, in about 1 to 90% preferably about 5 to 50%, R is CH₂OH, and in about 0 to 15%, preferably about 1 to 5%, R is R'COOCH₂wherein R'CO is the acyl group of a fatty acid of about 2 to 20, andpreferably about 8 to 18, carbon atoms or of a polycarboxylic acid,

(b) a curing agent for said polymer that is capable of crosslinking thepolymer; and

(c) a catalyst that catalyzes the reaction between the polymer and thecuring agent.

As is apparent from the above formula, the preferred polymer is acopolymer of alkylene oxide, glycidol and a glycidyl ester of a fattyacid or polycarboxylic acid, though the glycidyl ester moieties are notessential. The preferred polymer is of about 500 to about 20,000 andmost preferably about 3,000 to about 7,000 weight average molecularweight. Also preferred is a polymer wherein an average of about 1 toabout 2 glycidyl ester moieties are present for about each 5000 unit ofmolecular weight. Above about 20,000 molecular weight, the polymers areextremely difficult to handle and dealkylate and become impractical foruse herein.

The curing agent is preferably one that is capable of crosslinking thepolymer by reaction with the hydroxyl groups of the glycidol units. Suchagents are well known and include aldehydes, melamine-formaldehydecondensates, polycarboxylic acids and their anhydrides, polyisocyanates,polyepoxides, and the like.

The nature of the catalyst depends on the type of curing agent used.Thus, acidic materials, such as zinc fluoroborate, organosulfonic acids,phosphoric acid, ammonium sulfate or persulfate or the like areeffective to catalyze the reaction of carboxylic acids or anhydrides,epoxides, aldehydes and melamine-formuladehyde condensates whiletertiary amines and other bases are effective with isocyanates.

The above composition is conveniently applied to textile materials froman aqueous dispersion, the treated material is dried and the surfacecoating thus produced is then cured by a brief heat treatment. Thisfixes the composition on the fiber so that it is resistant to removal bynormal wear, laundering, drycleaning, and the like.

A major advantage of the invention is that many of the polymers used inthe composition are water-soluble or sufficiently surface-active to beself-emulsifying in water, thus eliminating need for a separatesurfactant. A related advantage is that the composition in the form ofan aqueous solution or emulsion can be applied to only one side of atextile product, such as cloth or carpet, and will penetrate through thetextile, thus becoming effectively distributed to the opposite side andto the individual fibers or threads constituting the textile product.

The flexibility inherent in the invention by virtue of the widevariation in number and size of ester groups and in the frequency ofcrosslinks in the cured composition, as well as in the relativeproportions of alkylene oxide and glycidol units in the polymer, permitswide variation and precise control of the effect of the antistatictreatment on the textile material.

DETAILED DESCRIPTION OF THE INVENTION

While it is possible to apply the antistatic composition of theinvention to textile materials in the form of a solution or dispersionin an organic solvent, it is far more practical to avoid the use of suchsolvents and to use aqueous solutions or dispersions instead. Theconcentration can be varied widely, depending largely on the nature ofthe textile material to be treated and the weight pick-up desired on thetextile material. In a preferred application, such as on carpet made ofsynthetic fibers, such solutions or dispersions may suitably containabout 5 to 50 wt. % of the antistatic composition (total solids basis).While in most instances, the polymer component is adequatelywater-soluble or self-dispersing, conventional dispersing andemulsifying agents may also be used if desired.

The curing agent should be one that is unreactive in the compositionunder normal conditions but becomes reactive when the treated textilematerial is dried and subjected to a curing treatment. Such treatmentmay consist of heating to an elevated temperature. The amount of curingagent used should be adjusted to produce the desired degree ofcrosslinkage. Too little produces an inadequately cured product whichmay be sensitive to water or drycleaning solvents while too much maycause a harsh "hand" or excessive stiffness or brittleness of the fiberitself or the coating thereon. For adequate insolubilization of theresin, there should be an average of at least about two, and preferablythree or more, hydroxyl groups per molecule and enough curing agentshould be used to react with an average of at least about two suchgroups.

The catalyst used and suitable amounts thereof depend on the nature ofthe curing agent. In most cases the catalysts are of the acidic type,zine fluoroborate and toluenesulfonic acid being especially preferred.

The antistat composition is prepared by simply mechanically dispersingthe ingredients in a fluid medium, preferably water.

The composition may be applied to textile materials in any convenientmanner, such as by padding, dipping, spraying, etc. Application to filmsmay be made in the same manner except that in some instances it will bedesirable to pretreat such films by standard corona discharge techniquesto obtain good adhesion by the antistatic composition. The "pick-up" oramount of solids thus deposited on the substrate will depend primarilyon the concentration of solids in the treating composition and theamount of composition applied. When the application is by dipping orspraying, any excess can be squeezed out by squeeze-rolls or the like.The treated material may be dried at normal room temperature and thencured by heating or, advantageously, the drying and curing steps may becombined by passing the wet material into a heated space wherein thewater or other fluid is evaporated and the composition is cured by theheat treatment. Suitable temperatures and times will vary, depending onthe particular materials being processed. For example, nylon carpettypically may be dried and cured at 105° C. in about 5 to 20 minutes orat 200° C. in 4 to 8 minutes. Light fabrics require much less time.

The copolymers of alkylene oxide, glycidol and glycidyl ester can bemade by copolymerizing the monomers by the usual methods ofcopolymerizing alkylene oxides and substituted alkylene oxides,including glycidyl compounds. This method requires glycidol as astarting material, however, and this monomer is expensive and notreadily available. Moreover, its primary hydroxyl group enters into thepolymerization, thus leading to undesirable and excessive branching inthe product.

Another procedure for making the copolymers is that of copolymerizingalkylene oxide with a silicon ester of glycidol (U.S. Pat. No.3,446,757) or with epichlorohydrin (U.S. Pat. Nos. 3,578,719, 3,595,924and 3,666,671), hydrolyzing the copolymer, thus indirectly producing alinear copolymer of alkylene oxide and glycidol, and then partiallyesterifying the copolymer with the desired fatty acid.

A preferred procedure is that disclosed in the copending applicationscited above, wherein alkylene oxide is copolymerized with tert.-butylglycidyl ether, thus producing an essentially linear copolymer. Thetert.-butyl groups are then removed and, to the desired extent, replacedwith acyl groups, thus producing the desired copolymer for use in thepresent invention. The one-step removal of tert.-butyl groups andpartial esterfication of the resultant glycidol units is effected byheating a mixture of the polymeric ether, the appropriate amount of acidor anhydride and an acid catalyst, preferably an organosulfonic acid,such as toluenesulfonic acid. Isobutylene and water are byproducts andcan be collected and used to monitor the progress of the reaction. theremoval of tert.-butyl groups is usually substantially complete by thetime the desired degree of esterification has been effected. The acidused for esterification may be a single species or a mixture of two ormore species, and may be saturated or unsaturated.

While the above discussion refers to certain copolymers as being linear,it should be understood that this refers to the configuration of thepolyoxyalkylene chain of units of the formula

    --CH.sub.2 CHRO--

and not necessarily to the entire molecule. It is conventional to useinitiators or starter compounds in such polymerizations, these arecompounds having one or more active hydrogen atoms, i.e., atoms that arereactive with alkylene oxides. Typical initiators include alcohols,glycols, glycerol, sorbitol, phenols, carboxylic acids, primary andsecondary amines, ammonia and water. Those having more than two activehydrogen atoms inherently produce branched molecules, one branch arisingat the site of each active hydrogen atom in excess of two. Thus,initiators having only one active hydrogen atom, such as monohydricalcohols and phenols, produce straight-chain polymers terminated on oneend with a hydroxyl group, those having two active hydrogen atomsproduce straight-chain polymers terminated on both ends with hydroxylgroups, and those having three or more active hydrogen atoms producebranched polymers, each branch being a straight chain terminated on thedistal end with a hydroxyl group. In making the polymers for use in thepresent invention, any or all of the terminal hydroxyl groups may beesterified with acids as herein described.

SPECIFIC EMBODIMENTS OF THE INVENTION

The following examples illustrate the practice of the invention.

EXAMPLE 1

A polymer consisting essentially of a random sequence of an average ofabout 22 ethylene oxide units, 1.5 glycidol units and 1.0 glycidylstearate unit was made by the preferred method described above bycopolymerizing a mixture of ethylene oxide and tert.-butyl glycidylether in a molar ratio of 9:1, using ethylene glycol as the initiatorand KOH as the catalyst. The polymer had a molecular weight of about1300. This polymer was simultaneously dealkylated and esterified byheating it with a catalytic amount of toluenesulfonic acid and anequimolar amount of stearic acid. About 2.5 moles of isobutylene and 1.0mole of water were evolved, thus producing the desired copolymer.

An antistatic composition was prepared from the above copolymer bymixing 100 parts by weight of the copolymer, 400 parts of water, 4 parts(anhydrous basis) of zinc fluoroborate and 5 parts of amelamine-formaldehyde condensate sold under the tradename Cymel 303.This composition was sprayed on the reverse side of a nylon shag carpettufted on jute, the spray being applied in an amount sufficient tothoroughly wet the surface of the fabric. Due to the unique surfactantproperties of the copolymer used, the aqueous dispersion penetratedthrough the carpet and wet the face of the carpet sufficiently todrastically reduce the static build-up thereon. The wet carpet wassimultaneously dried and cured by heating in a circulating oven at 150°C. for 25 minutes. It was then back-sized with a conventional elastomerlatex and again dried.

The static build-up of the treated carpet and of a control sample of thesame carpet treated the same way except that no antistatic compositionwas applied thereto was determined by AATCC Method 134-1969. The controlsample developed a charge of 12,300 volts whereas the treated exampledeveloped only 6100 volts.

EXAMPLE 2

A copolymer of molecular weight 5000 was prepared as described abovefrom a 75:25 molar ratio of ethylene oxide and tert.-butyl glycidylether. It was then dealkylated and partially esterified with 1.5 molarequivalents of stearic acid, thus producing a copolymer containing ineach molecule an average of about 57 ethylene oxide units, 17.5 glycidolunits and 1.5 glycidyl stearate units. A composition similar to thatused in Example 1 was prepared as a 20% solids dispersion of thecopolymer in water together with 5% of the Cymel curing agent and 4% ofthe zinc fluoroborate catalyst (both based on copolymer). This wasapplied to a polyester fabric in an amount to provide a 1% by weightpick-up. After being dried and cured in a 150° C. oven the surfaceresistivity (static-build-up tendency) was compared to that of a 80 × 80cotton fabric, both fabrics having been conditioned at 24° C. and 20%relative humidity. The resistivity of the cotton was 8 × 10¹¹ ohms whilethat of the treated polyester was 3 × 10¹⁰ ohms.

EXAMPLE 3

A copolymer of molecular weight 5000, initiated with water, was preparedas described above from a 90:10 molar ratio of ethylene oxide andtert.-butyl glycidyl ether. It was then dealkylated and partiallyesterified with 1 molar equivalent of stearic acid, thus producing acopolymer containing in each molecule an average of about 90 ethyleneoxide units, 9 glycidol units and 1 glycidyl stearate unit. Acomposition similar to that used in Example 1 was prepared as a 20%solids dispersion of the copolymer in water together with about 10% ofthe Cymel curing agent and about 6.5% of the zinc fluoroborate catalyst(both based on copolymer weight). This was applied to a polyester fabricin an amount to provide about 1-2 weight % pick-up. After being driedand cured in a 115° C. oven, the surface resistivity was about 6 × 10⁹ohms. For the untreated fabric, the reading was off scale, i.e., greaterthan 10¹⁵ ohms.

EXAMPLE 4

A copolymer of molecular weight 3000, initiated with dodecyl alcohol,was prepared as described above from a 75:25 molar ratio of ethyleneoxide and tert.-butyl glycidyl ether. After complete dealkylation, thedealkylated copolymer was used to prepare a 20% solid dispersion inwater together with about 5% of the Cymel curing agent and about 5% zincfluoroborate catalyst (both based on copolymer weight). Afterapplication to a polyester fabric, drying and curing in the manner ofExample 3, the surface resistivity was about 1 × 10¹¹ ohms versusgreater than 10¹⁵ ohms for the untreated fabric.

We claim:
 1. A topical antistatic composition for use on a substrate toimpart antistatic properties thereto, said composition comprising(a) apolymer of less than about 20,000 molecular weight consistingessentially of units of the formula

    --CH.sub.2 CHRO--

where in about 10% to 99% of the units R is H, CH₃ or C₂ H₅, in about 1%to 90% R is CH₂ OH, and in about 0% to 15% R is R'COOCH₂, wherein R'COis the acyl radical of a fatty acid of about 2 to 20 carbon atoms or apolycarboxylic acid, (b) a curing agent for said polymer having aplurality of groups reactive with primary hydroxyl groups, and (c) acatalyst that catalyzes the reaction between the polymer and the curingagent.
 2. The composition of claim 1 wherein the curing agent is amelamine-formaldehyde condensate.
 3. The composition of claim 1 whereinthe catalyst is toluenesulfonic acid.
 4. The composition of claim 1where in at least one --CH₂ CHRO-- unit, R is R'COOCH₂.
 5. A process forreducing the tendency of a substrate to accumulate an electric chargecomprising(a) applying to the substrate a composition of claim 1 and (b)curing said composition on the substrate.
 6. The process of claim 5wherein the curing agent is a melamine-formaldehyde condensate.
 7. Theprocess of claim 6 wherein the catalyst is toluenesulfonic acid.
 8. Theprocess of claim 5 wherein the substrate is a textile material.
 9. Theprocess of claim 5 wherein the substrate is carpet.
 10. An article thathas been treated by the process of claim 5 wherein the substrate is atextile material.
 11. The process of claim 10 wherein at least one --CH₂CHRO-- unit, R is R'COOCH₂ and at least one R' is the C₁₇ H₃₅ residue ofstearic acid.
 12. The composition of claim 4 wherein at least one R' isthe C₁₇ H₃₅ residue of stearic acid.
 13. The composition of claim 1wherein the polymer is essentially linear.